Waterproof 230V connector needed

[Lobster]

I want wire a permanent extension cable to my car battery charger, so I can plug it in to my outdoor mains socket and connect it to the battery as required, with minimum fuss. Struggling to find an appropriate item though.

I think

may be the sort of thing? Not sure about that particular one as I worry about the provenance of some electrical stuff on ebay, and an outdoor connector would be right up there.

My charger has a two-core, flat-profile flex - will that work OK with the circular rubber glands these things usually have?

Any suggestions very welcome - preferably not from a supplier with a huge minimum shipping fee (I do have a local Screwfix and Toolstation)

Thanks

[Tricky Dicky]

Why not just replace the whole cable, it will probably work out cheaper and you do not have to worry about potential leakage.

Richard

[Tim Watts]

The connector is fine.

However the gland may not be terribly effective with flat flex.

Given the battery charger is not waterproof, I'd cut the flex close to it and joint it there.

Another option is to crimp or solder, heatshrink the joints then put adhesive lined heatshrink over the whole lot. That will make a watertight joint.

[Roger Mills]

Presumably the charger itself will be protected from the weather? In that case - as others have said - simply replace the existing cable with a much longer one. Then you don't have to worry about waterproof connectors.

[John Rumm]

I would just replace the whole flex...

One thing to consider, those small flat flexes are usually only fault protected by a 13A fuse when they are no longer than about 6'. So if extending it with something similar, you would need to make sure a smaller fuse is fitted to the plug. (or use a heavier flex). CPC sell rubber clad flex by the meter...

[Dave Plowman (News)]

Given you can't leave the charger in the rain, etc, why do you need a waterproof connector? Use an extension lead and just put the ordinary 13 amp one under the bonnet or boot along with the charger. You then have the extension lead for other things if needed.

Another way you might consider. Given how cheap those Lidl etc chargers are, I've built one into my old Rover. Alongside the spare wheel in its underfloor space, as there's room there and its protected from being bashed. But it could go anywhere. I used a waterproof mains connector (Buccaneer) fitted to the panel under the rear bumper, so nearly invisible.

[Robin]

I'm glad you asked that as it's what I do :)

[Lobster]

On 22 Feb 2016, John Rumm grunted:

Thanks for the replies

I would but would have to trash the charger in doing so - however it does make perfect sense to use a simple non-waterproof connector close to the charger as has also been suggested!

Hadn't appreciated that aspect. Actually I'm going to need 17m of flex to get from my exterior plug to the car. The charger is 60W, and was supplied with a 3A fuse. What's the implications there?

Basically, I have hitherto been using this charger with a cable reel, which has an RCD unit at the plug end, meaning that I can't use my exterior socket as the RCD won't fit into the weatherproof box. Therefore I have to prat about running the cable reel through a window instead, which is crap especially overnight or in bad weather (which is usually the case when the battery needs charging!) Hence my idea for the dedicated extension.

[Dave Plowman (News)]

Get (or make) an ordinary extension (not on a reel). If you can't fit an RCD plug to your outside socket, no worse than plugging in the charger direct.

But IMHO any outside socket should be RCD protected. Before I changed to an RCD CU, I had a RCD mounted close to the outside socket for this purpose. It's rather like an FCU and as well as the RCD has a 13 amp fuse in it. And can be used to switch off the outside socket.

[Lobster]

On 24 Feb 2016, "Dave Plowman (News)" grunted:

Oh, +1

We do have an RCD CU already so the unit on my cable reel is actually redundant at home - I have this model because I use it at other (non-RCD- protected) locations.

I just kind of liked the idea of having my charger hard-wired with the correct length of cable to be able to use it, so I don't need to track down the extension cable when the car battery's flat. I also have a bit of an aversion to using extensions with appliances on a permanant basis (hence the rather large number of mains sockets in my house!)

[Dave Plowman (News)]

Personally I have an aversion to any form of flex connector. If I can't replace the entire flex, I'll stick to a plug and socket.

I really can't see the problem. The charger will have to go under the bonnet etc if it's likely to get wet. So what's wrong with having a 13 amp plug and socket from an extension there too? It's what I do.

[John Rumm]

Is it welded together then?

3A flex is typically 0.5mm CSA core size, which is say 39mOhm/m. You are talking about a L to N short at the end of the cable of length 17m, so that's a round trip resistance of about 1.32 ohms. Add that to the 1.5 ohm max loop impedance for a ring protected with a B32 MCB, and it gives you 2.82 ohms total. So your prospective fault current could be as low as 230 / 2.82 = 81A

That will open a 13A fuse in about a second worst case (i.e. too slowly for a portable appliance). Just to add insult to injury you can do a quick with the adiabatic equation: s = sqrt( i^2 t ) / k where k is 115 for PVC clad cables.

s = sqrt( 6561 ) / 115 = 0.7mm^2

Would suggest that the flex may burst into flames before the fuse has got round to doing its thing!

With a 3A fuse however you should be safely down in the 0.1 sec or less opening time, and hence only need about 0.2mm of CSA to survive for that long.

(having said that, you don't have to use 0.5mm^2 flex, you could go up a size anyway)

[Martin Bonner]

Follow you so far (I don't have the resistance of various cables memorized, but I can see how to google for it; similarly the 1.5 Ohm feels like something that I ought to be able to find in the IEEE regs and probably lots of other places).

But I don't know where to get that information from. Is it another table in the regs?

Or is it arcane knowledge that you are only allowed to know once accepted in the secret Electricians Society.

[charles]

[Snip]

IEEE are American, presumably you ment IET (as it is now) or even BS7671.

[John Rumm]

1.5 is actually a slight over estimate, BS7671 has 1.44 for a B32 MCB:

You should also find it in the on site guide and a number of other places. You could also work it out from first principles by looking at the response curves for the MCB:

(or for that matter, just remember that for a type B device the fault trip current will be 5 x In (10x for a type C and 15x for a type D). So

5 x 32 = 160A)

Since we know the current needed to guarantee "instant" opening of a B32 MCB (i.e. using its magnetic fault detection response rather than its overload thermal response) is 160A. A quick application of V = IR, so

230 = 160 R, 230 / 160 = 1.44 Ohms.

That one is not in the regs, but you will find it in BS1362, and also here:

(click picture for larger size)

There are loads of bits of obscure information tucked away in various BS docs. Alas they are not that well publicised and not always easy to get hold of without paying silly money for. (local library is the best bet - some also allow free online access to library card holders via the BSI web site)

[ARW]

Small typo correction - it is 20x for a type D.

[John Rumm]

Indeed you are right. That was not even a typo, it was me remembering wrong!